BMS for balance charger

[Nearchos]

Two newbie questions:

a) is it possible to have an electric bicycle that charges with a balance charger but also has a BMS in the battery pack?
Is it not possible to regulate the BMS Not to balance the cells while charging the battery, but only balance the cells while the battery is not connected to a charger?

b) is there any difference between a
i) pulse
and a
ii) balance

charger?

 

[docw009]

I don't think there are any 13S balance chargers. I have a 6S Sky AC B6 RC balance charger abd I have hooked it up to six banks of a 13S battery with the original BMS still attached. I had to make a cable that connected to the six P-groups. I did this to see if it would balance any faster than the resident BMS. Results inconclusive,

 

[Nearchos]

Is a pulse and a balance charger the same?

 

[amberwolf]

a) is it possible to have an electric bicycle that charges with a balance charger but also has a BMS in the battery pack?
Is it not possible to regulate the BMS Not to balance the cells while charging the battery, but only balance the cells while the battery is not connected to a charger?

Those are two separate questions, so:

First, you can always choose to add a separate balance connector for your battery, wired to the cells just like the balance/sense connector from your BMS. Then you also add a separate main +/- from the block of cells (spearate from the ones to the BMS). Then use those for the external balance charger, per that charger's instructions.

Second, if you have a smart BMS (like the various bluetooth types), it may have an option in the app to turn on or off the balancing function manually. Whether this will allow balancing when not charging depends on the settings available in the app, and how the balancers work in the BMS.

There are two types of balancers:

The most common is passive resistive "shunts" that simply drain down high cells above some setpoint, until they reach a second setpoint. Any cell below those points will not be altered, so if it's lower than the others it will remain so, if no charging current is flowing to continue filling it up.

Active charge-shuffling is becoming more common, and this can operate at any time, moving charge from high cells to low cells, depending on the setpoints provided.

You'd need to buy the BMS with the type of balancing you want, and the type and amount of control over it you want.


There are also BMS that do not have balancers at all, but only protection circuitry. (these are often used in cheap battery packs, which is one reason the cheaper the pack is, the worse it tends to perform, becuase it's alreayd made of cells that wont' stay balanced because they're very different from each other, and wihtout something to help rebalance them they get worse and worse on every usage cycle).

b) is there any difference between a
i) pulse
and a
ii) balance

charger?

Without a link to one to show us what you mean by "pulse charger", the only thing I can think of that could be described as that would be a desulfation device for lead-acid, which uses pulses of higher voltage to attempt to remove the crystals that form in lead-acid batteries that short out the plates.

If that's what the pulse charger you are thinking of does, then it is very different from a balance charger, and is not meant to be used on lithium packs.

 

[lnanek]

I've seen some 20s and 24s balance chargers, but they cost over a thousand dollars.

There are some old RC chargers that support master and slave connections as well to use multiple at once. These are quite cheap on eBay, but I never figured out of they could be treated as isolated or not. E.g:

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Basically, as long as the power supplies are isolated, you can charge an 18s battery with three 6s chargers. Just wire up each charger to each block of 6 p-groups in the battery. If they are not isolated, however, this doesn't work. Which means it can be tough hunting down things like dual 8s chargers on eBay and knowing if you can use both sides at once for different halves of the same battery.

 

[Nearchos]

Those are two separate questions, so:

First, you can always choose to add a separate balance connector for your battery, wired to the cells just like the balance/sense connector from your BMS. Then you also add a separate main +/- from the block of cells (spearate from the ones to the BMS). Then use those for the external balance charger, per that charger's instructions.

Second, if you have a smart BMS (like the various bluetooth types), it may have an option in the app to turn on or off the balancing function manually. Whether this will allow balancing when not charging depends on the settings available in the app, and how the balancers work in the BMS.

There are two types of balancers:

The most common is passive resistive "shunts" that simply drain down high cells above some setpoint, until they reach a second setpoint. Any cell below those points will not be altered, so if it's lower than the others it will remain so, if no charging current is flowing to continue filling it up.

Active charge-shuffling is becoming more common, and this can operate at any time, moving charge from high cells to low cells, depending on the setpoints provided.

You'd need to buy the BMS with the type of balancing you want, and the type and amount of control over it you want.


There are also BMS that do not have balancers at all, but only protection circuitry. (these are often used in cheap battery packs, which is one reason the cheaper the pack is, the worse it tends to perform, becuase it's alreayd made of cells that wont' stay balanced because they're very different from each other, and wihtout something to help rebalance them they get worse and worse on every usage cycle).


Without a link to one to show us what you mean by "pulse charger", the only thing I can think of that could be described as that would be a desulfation device for lead-acid, which uses pulses of higher voltage to attempt to remove the crystals that form in lead-acid batteries that short out the plates.

If that's what the pulse charger you are thinking of does, then it is very different from a balance charger, and is not meant to be used on lithium packs.

Perhaps the "pulse" charger was a bad translation from Chinese. Thanks a lot for your input!